The present invention relates generally to interconnection systems, and, more particularly, to alignment tolerant dense optical interconnect systems which incorporate the use of rod lenses. With the advent of substantial new performance levels in high bandwidth digital and analog electro-optic systems, there exists a greater need to provide dense, alignment tolerant interconnection capability. This is especially true in digital computing systems; in analog systems such as phased array radar; and in high bandwidth optical carriers in communication systems. However, it should be realized that these are just several of numerous systems which benefit from application of high-bandwidth electro-optic interconnection.
In many current and future systems light beams are modulated in a digital and/or analog fashion and used as xe2x80x9coptical carriersxe2x80x9d of information. There are many reasons why light beams or optical carriers are preferred in these applications. For example, as the data rate required of such channels increases, the high optical frequencies provide a tremendous improvement in available bandwidth over conventional electrical channels such as formed by wires and coaxial cables. In addition, the energy required to drive and carry high bandwidth signals can be reduced at optical frequencies. Further, optical channels, even those propagating in free space (without waveguides such as optical fibers) can be packed closely and even intersect in space with greatly reduced crosstalk between channels.
Conventional electrical interconnection over wires or traces is reaching severe performance limits due to density, power, crosstalk, time delay, and complexity. For example, chip scaling continues to provide for a doubling of transistors on a chip every 18 months. A 2 cmxc3x972 cm chip currently requires 2 km of wires or traces for interconnection with 6 layers of metal and the complexity exponentiates with the number of metal layers. With designs using 0.18 micron wires, 60% of the delay is from the interconnects themselves. In shrinking from 0.5 micron wires to 0.18 micron wires on chip, the rc time constant increases by a factor of 10. Using optical interconnection, the power dissipation does not scale with the length of interconnection, and optical interconnects are superior for short signal rise times. Similar advantages of optical interconnection over electrical interconnection pertain to longer range interconnection, e.g., from chip-to-chip, intra-board, inter-board, and computer-to-peripheral.
Other optical interconnect approaches suffer from critical alignment tolerances; restrictive focusing, component separation and vibration tolerance requirements; insertion loss which limits speed and power efficiency; bulky and large-footprint optical systems; limited density and scalability; lack of physical flexibility and compliance of the interconnect, and the need to provide an excessively protective environment in order to maintain optical alignment over time.
It is therefore an object of this invention to provide a high density (many parallel interconnected channels in a small volume) optical interconnect system that can optically interconnect tens, hundreds, or thousands of high-bandwidth channels with a technology that is flexible and alignment tolerant.
It is another object of this invention to provide a high density optical interconnect system in which the component optical and electro-optical components are arranged in a single monolithic unit.
It is another object of this invention to provide a high density optical interconnect system that provides a nearly lossless one-to-one optical interconnection from a set of input channels to a set of output channels.
It is another object of this invention to provide a high density optical interconnect system that, by virtue of its low insertion loss, can provide very high-speed bidirectional interconnection among dense two-dimensionally packed interconnected channels.
It is another object of this invention to provide a high density optical interconnect system that can interconnect over distances spanning millimeters to tens of meters or longer.
It is further an object of this invention to provide a high density optical interconnect system that can be pre-aligned during manufacture and is thus readily fieldable by non-optically trained personnel.
It is further an object of this invention to provide a high density optical interconnect across single die or integrated circuit substrate, inside multi-chip modules, between die, between modules or components, between boards, between computers, between computers and peripherals, or between peripherals.
It is still further an object of this invention to provide a high density optical interconnect system that uses a small fraction of device area that would be required for arrays of traces, wires, or waveguides.
It is still further an object of this invention to provide a high density optical interconnect system that is capable of bending and flexing to accommodate components that shift relative to each other while maintaining interconnection of many parallel optical channels among the shifting components.
It is still further an object of this invention to provide a high density optical interconnect system that interconnects many parallel optical channels among components while maintaining relative insensitivity to longitudinal and lateral shifts between the interconnected components.
It is still further an object of this invention to provide a high density optical interconnect system that can be disconnected and reconnected simply while maintaining alignment among many parallel optical channels.
It is still further an object of this invention to provide a high density optical interconnect system that provides for a uniform delay for all channels, thus minimizing relative signal skews.
The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention described hereinbelow.
The present invention overcomes problems associated with size, power, crosstalk, and speed associated with conventional electrical interconnects, and overcomes problems with alignment tolerance in conventional optical interconnection. In a preferred embodiment of The optical interconnect system or optical data pipe approach of the present invention, although not limited thereto, mating emitter and detector arrays are pre-aligned and fixed on or near the ends of a gradient index rod imager, and this flexible pre-aligned structure is then mounted to the host. Using this technology, which includes the various embodiments of this invention, hundreds or thousands of high bandwidth channels can be interconnected for short distances (intra-die, between neighboring chips or MCMs) or over relatively long distances (full board wrap-around, board-to-board, computer to peripheral, computer to computer, etc.). The optical interconnect system of this invention provides a nearly lossless one-to-one optical interconnection from a set of input channels to a set of output channels, and supports extreme density, low power, and low crosstalk for high bandwidth signals.
One of many advantages of the system of this invention is that it can be pre-aligned and fixed during manufacture (e.g., using automated alignment and cementing procedures) to produce optical interconnects that have greatly relaxed alignment tolerances and are thus readily), usable in the field by non-optical personnel. The interconnection systems of the present invention are thus tolerant of handling, bending and displacements among interconnected components without losing their function of interconnecting many closely packed (dense) optical channels. Other advantages of this invention late to the fact that it is tolerant of misalignments, vibrations, etc.
For a better understanding of the present invention, together with other and further objects, reference is made to the following description taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended claims.